1. First remove the rear extension cover of the gearbox. After removing the above speed sensor and bolts, the rear extension box can be removed with a hammer.
2. Remove the fuel tank and gasket, and at the same time remove the gasket that fixes the intermediate shaft.
3. Remove the four screws blocking the small cover, and the small cover can be removed by tapping with a hammer.
4. Remove the reverse fixing screw with six internal corners. The screw cannot be removed without removing the gear box.
5. After the gearbox is removed, remove the whole gear and shaft, and you can see the oil seal. Just pry off the oil seal and install a new one.